net/mptcp/options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Multipath TCP
   3  *
   4  * Copyright (c) 2017 - 2019, Intel Corporation.
   5  */
   6
   7 #define pr_fmt(fmt) "MPTCP: " fmt
   8
   9 #include <linux/kernel.h>
  10 #include <crypto/sha2.h>
  11 #include <net/tcp.h>
  12 #include <net/mptcp.h>
  13 #include "protocol.h"
  14 #include "mib.h"
  15
  16 #include <trace/events/mptcp.h>
  17
  18 static bool mptcp_cap_flag_sha256(u8 flags)
  19 {
  20         return (flags & MPTCP_CAP_FLAG_MASK) == MPTCP_CAP_HMAC_SHA256;
  21 }
  22
  23 static void mptcp_parse_option(const struct sk_buff *skb,
  24                                const unsigned char *ptr, int opsize,
  25                                struct mptcp_options_received *mp_opt)
  26 {
  27         u8 subtype = *ptr >> 4;
  28         int expected_opsize;
  29         u8 version;
  30         u8 flags;
  31         u8 i;
  32
  33         switch (subtype) {
  34         case MPTCPOPT_MP_CAPABLE:
  35                 /* strict size checking */
  36                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
  37                         if (skb->len > tcp_hdr(skb)->doff << 2)
  38                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
  39                         else
  40                                 expected_opsize = TCPOLEN_MPTCP_MPC_ACK;
  41                 } else {
  42                         if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)
  43                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYNACK;
  44                         else
  45                                 expected_opsize = TCPOLEN_MPTCP_MPC_SYN;
  46                 }
  47
  48                 /* Cfr RFC 8684 Section 3.3.0:
  49                  * If a checksum is present but its use had
  50                  * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
  51                  * close the subflow with a RST, as it is not behaving as negotiated.
  52                  * If a checksum is not present when its use has been negotiated, the
  53                  * receiver MUST close the subflow with a RST, as it is considered
  54                  * broken
  55                  * We parse even option with mismatching csum presence, so that
  56                  * later in subflow_data_ready we can trigger the reset.
  57                  */
  58                 if (opsize != expected_opsize &&
  59                     (expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
  60                      opsize != TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM))
  61                         break;
  62
  63                 /* try to be gentle vs future versions on the initial syn */
  64                 version = *ptr++ & MPTCP_VERSION_MASK;
  65                 if (opsize != TCPOLEN_MPTCP_MPC_SYN) {
  66                         if (version != MPTCP_SUPPORTED_VERSION)
  67                                 break;
  68                 } else if (version < MPTCP_SUPPORTED_VERSION) {
  69                         break;
  70                 }
  71
  72                 flags = *ptr++;
  73                 if (!mptcp_cap_flag_sha256(flags) ||
  74                     (flags & MPTCP_CAP_EXTENSIBILITY))
  75                         break;
  76
  77                 /* RFC 6824, Section 3.1:
  78                  * "For the Checksum Required bit (labeled "A"), if either
  79                  * host requires the use of checksums, checksums MUST be used.
  80                  * In other words, the only way for checksums not to be used
  81                  * is if both hosts in their SYNs set A=0."
  82                  */
  83                 if (flags & MPTCP_CAP_CHECKSUM_REQD)
  84                         mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
  85
  86                 mp_opt->deny_join_id0 = !!(flags & MPTCP_CAP_DENY_JOIN_ID0);
  87
  88                 mp_opt->suboptions |= OPTIONS_MPTCP_MPC;
  89                 if (opsize >= TCPOLEN_MPTCP_MPC_SYNACK) {
  90                         mp_opt->sndr_key = get_unaligned_be64(ptr);
  91                         ptr += 8;
  92                 }
  93                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK) {
  94                         mp_opt->rcvr_key = get_unaligned_be64(ptr);
  95                         ptr += 8;
  96                 }
  97                 if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
  98                         /* Section 3.1.:
  99                          * "the data parameters in a MP_CAPABLE are semantically
 100                          * equivalent to those in a DSS option and can be used
 101                          * interchangeably."
 102                          */
 103                         mp_opt->suboptions |= OPTION_MPTCP_DSS;
 104                         mp_opt->use_map = 1;
 105                         mp_opt->mpc_map = 1;
 106                         mp_opt->data_len = get_unaligned_be16(ptr);
 107                         ptr += 2;
 108                 }
 109                 if (opsize == TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM) {
 110                         mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
 111                         mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 112                         ptr += 2;
 113                 }
 114                 pr_debug("MP_CAPABLE version=%x, flags=%x, optlen=%d sndr=%llu, rcvr=%llu len=%d csum=%u",
 115                          version, flags, opsize, mp_opt->sndr_key,
 116                          mp_opt->rcvr_key, mp_opt->data_len, mp_opt->csum);
 117                 break;
 118
 119         case MPTCPOPT_MP_JOIN:
 120                 mp_opt->suboptions |= OPTIONS_MPTCP_MPJ;
 121                 if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 122                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 123                         mp_opt->join_id = *ptr++;
 124                         mp_opt->token = get_unaligned_be32(ptr);
 125                         ptr += 4;
 126                         mp_opt->nonce = get_unaligned_be32(ptr);
 127                         ptr += 4;
 128                         pr_debug("MP_JOIN bkup=%u, id=%u, token=%u, nonce=%u",
 129                                  mp_opt->backup, mp_opt->join_id,
 130                                  mp_opt->token, mp_opt->nonce);
 131                 } else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
 132                         mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 133                         mp_opt->join_id = *ptr++;
 134                         mp_opt->thmac = get_unaligned_be64(ptr);
 135                         ptr += 8;
 136                         mp_opt->nonce = get_unaligned_be32(ptr);
 137                         ptr += 4;
 138                         pr_debug("MP_JOIN bkup=%u, id=%u, thmac=%llu, nonce=%u",
 139                                  mp_opt->backup, mp_opt->join_id,
 140                                  mp_opt->thmac, mp_opt->nonce);
 141                 } else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
 142                         ptr += 2;
 143                         memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 144                         pr_debug("MP_JOIN hmac");
 145                 } else {
 146                         mp_opt->suboptions &= ~OPTIONS_MPTCP_MPJ;
 147                 }
 148                 break;
 149
 150         case MPTCPOPT_DSS:
 151                 pr_debug("DSS");
 152                 ptr++;
 153
 154                 /* we must clear 'mpc_map' be able to detect MP_CAPABLE
 155                  * map vs DSS map in mptcp_incoming_options(), and reconstruct
 156                  * map info accordingly
 157                  */
 158                 mp_opt->mpc_map = 0;
 159                 flags = (*ptr++) & MPTCP_DSS_FLAG_MASK;
 160                 mp_opt->data_fin = (flags & MPTCP_DSS_DATA_FIN) != 0;
 161                 mp_opt->dsn64 = (flags & MPTCP_DSS_DSN64) != 0;
 162                 mp_opt->use_map = (flags & MPTCP_DSS_HAS_MAP) != 0;
 163                 mp_opt->ack64 = (flags & MPTCP_DSS_ACK64) != 0;
 164                 mp_opt->use_ack = (flags & MPTCP_DSS_HAS_ACK);
 165
 166                 pr_debug("data_fin=%d dsn64=%d use_map=%d ack64=%d use_ack=%d",
 167                          mp_opt->data_fin, mp_opt->dsn64,
 168                          mp_opt->use_map, mp_opt->ack64,
 169                          mp_opt->use_ack);
 170
 171                 expected_opsize = TCPOLEN_MPTCP_DSS_BASE;
 172
 173                 if (mp_opt->use_ack) {
 174                         if (mp_opt->ack64)
 175                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK64;
 176                         else
 177                                 expected_opsize += TCPOLEN_MPTCP_DSS_ACK32;
 178                 }
 179
 180                 if (mp_opt->use_map) {
 181                         if (mp_opt->dsn64)
 182                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP64;
 183                         else
 184                                 expected_opsize += TCPOLEN_MPTCP_DSS_MAP32;
 185                 }
 186
 187                 /* Always parse any csum presence combination, we will enforce
 188                  * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 189                  */
 190                 if (opsize != expected_opsize &&
 191                     opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
 192                         break;
 193
 194                 mp_opt->suboptions |= OPTION_MPTCP_DSS;
 195                 if (mp_opt->use_ack) {
 196                         if (mp_opt->ack64) {
 197                                 mp_opt->data_ack = get_unaligned_be64(ptr);
 198                                 ptr += 8;
 199                         } else {
 200                                 mp_opt->data_ack = get_unaligned_be32(ptr);
 201                                 ptr += 4;
 202                         }
 203
 204                         pr_debug("data_ack=%llu", mp_opt->data_ack);
 205                 }
 206
 207                 if (mp_opt->use_map) {
 208                         if (mp_opt->dsn64) {
 209                                 mp_opt->data_seq = get_unaligned_be64(ptr);
 210                                 ptr += 8;
 211                         } else {
 212                                 mp_opt->data_seq = get_unaligned_be32(ptr);
 213                                 ptr += 4;
 214                         }
 215
 216                         mp_opt->subflow_seq = get_unaligned_be32(ptr);
 217                         ptr += 4;
 218
 219                         mp_opt->data_len = get_unaligned_be16(ptr);
 220                         ptr += 2;
 221
 222                         if (opsize == expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
 223                                 mp_opt->suboptions |= OPTION_MPTCP_CSUMREQD;
 224                                 mp_opt->csum = get_unaligned((__force __sum16 *)ptr);
 225                                 ptr += 2;
 226                         }
 227
 228                         pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u",
 229                                  mp_opt->data_seq, mp_opt->subflow_seq,
 230                                  mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
 231                                  mp_opt->csum);
 232                 }
 233
 234                 break;
 235
 236         case MPTCPOPT_ADD_ADDR:
 237                 mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 238                 if (!mp_opt->echo) {
 239                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
 240                             opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT)
 241                                 mp_opt->addr.family = AF_INET;
 242 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 243                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6 ||
 244                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT)
 245                                 mp_opt->addr.family = AF_INET6;
 246 #endif
 247                         else
 248                                 break;
 249                 } else {
 250                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE ||
 251                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT)
 252                                 mp_opt->addr.family = AF_INET;
 253 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 254                         else if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE ||
 255                                  opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT)
 256                                 mp_opt->addr.family = AF_INET6;
 257 #endif
 258                         else
 259                                 break;
 260                 }
 261
 262                 mp_opt->suboptions |= OPTION_MPTCP_ADD_ADDR;
 263                 mp_opt->addr.id = *ptr++;
 264                 mp_opt->addr.port = 0;
 265                 mp_opt->ahmac = 0;
 266                 if (mp_opt->addr.family == AF_INET) {
 267                         memcpy((u8 *)&mp_opt->addr.addr.s_addr, (u8 *)ptr, 4);
 268                         ptr += 4;
 269                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR_PORT ||
 270                             opsize == TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT) {
 271                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 272                                 ptr += 2;
 273                         }
 274                 }
 275 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 276                 else {
 277                         memcpy(mp_opt->addr.addr6.s6_addr, (u8 *)ptr, 16);
 278                         ptr += 16;
 279                         if (opsize == TCPOLEN_MPTCP_ADD_ADDR6_PORT ||
 280                             opsize == TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT) {
 281                                 mp_opt->addr.port = htons(get_unaligned_be16(ptr));
 282                                 ptr += 2;
 283                         }
 284                 }
 285 #endif
 286                 if (!mp_opt->echo) {
 287                         mp_opt->ahmac = get_unaligned_be64(ptr);
 288                         ptr += 8;
 289                 }
 290                 pr_debug("ADD_ADDR%s: id=%d, ahmac=%llu, echo=%d, port=%d",
 291                          (mp_opt->addr.family == AF_INET6) ? "6" : "",
 292                          mp_opt->addr.id, mp_opt->ahmac, mp_opt->echo, ntohs(mp_opt->addr.port));
 293                 break;
 294
 295         case MPTCPOPT_RM_ADDR:
 296                 if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 297                     opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 298                         break;
 299
 300                 ptr++;
 301
 302                 mp_opt->suboptions |= OPTION_MPTCP_RM_ADDR;
 303                 mp_opt->rm_list.nr = opsize - TCPOLEN_MPTCP_RM_ADDR_BASE;
 304                 for (i = 0; i < mp_opt->rm_list.nr; i++)
 305                         mp_opt->rm_list.ids[i] = *ptr++;
 306                 pr_debug("RM_ADDR: rm_list_nr=%d", mp_opt->rm_list.nr);
 307                 break;
 308
 309         case MPTCPOPT_MP_PRIO:
 310                 if (opsize != TCPOLEN_MPTCP_PRIO)
 311                         break;
 312
 313                 mp_opt->suboptions |= OPTION_MPTCP_PRIO;
 314                 mp_opt->backup = *ptr++ & MPTCP_PRIO_BKUP;
 315                 pr_debug("MP_PRIO: prio=%d", mp_opt->backup);
 316                 break;
 317
 318         case MPTCPOPT_MP_FASTCLOSE:
 319                 if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 320                         break;
 321
 322                 ptr += 2;
 323                 mp_opt->rcvr_key = get_unaligned_be64(ptr);
 324                 ptr += 8;
 325                 mp_opt->suboptions |= OPTION_MPTCP_FASTCLOSE;
 326                 pr_debug("MP_FASTCLOSE: recv_key=%llu", mp_opt->rcvr_key);
 327                 break;
 328
 329         case MPTCPOPT_RST:
 330                 if (opsize != TCPOLEN_MPTCP_RST)
 331                         break;
 332
 333                 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 334                         break;
 335
 336                 mp_opt->suboptions |= OPTION_MPTCP_RST;
 337                 flags = *ptr++;
 338                 mp_opt->reset_transient = flags & MPTCP_RST_TRANSIENT;
 339                 mp_opt->reset_reason = *ptr;
 340                 pr_debug("MP_RST: transient=%u reason=%u",
 341                          mp_opt->reset_transient, mp_opt->reset_reason);
 342                 break;
 343
 344         case MPTCPOPT_MP_FAIL:
 345                 if (opsize != TCPOLEN_MPTCP_FAIL)
 346                         break;
 347
 348                 ptr += 2;
 349                 mp_opt->suboptions |= OPTION_MPTCP_FAIL;
 350                 mp_opt->fail_seq = get_unaligned_be64(ptr);
 351                 pr_debug("MP_FAIL: data_seq=%llu", mp_opt->fail_seq);
 352                 break;
 353
 354         default:
 355                 break;
 356         }
 357 }
 358
 359 void mptcp_get_options(const struct sk_buff *skb,
 360                        struct mptcp_options_received *mp_opt)
 361 {
 362         const struct tcphdr *th = tcp_hdr(skb);
 363         const unsigned char *ptr;
 364         int length;
 365
 366         /* initialize option status */
 367         mp_opt->suboptions = 0;
 368
 369         length = (th->doff * 4) - sizeof(struct tcphdr);
 370         ptr = (const unsigned char *)(th + 1);
 371
 372         while (length > 0) {
 373                 int opcode = *ptr++;
 374                 int opsize;
 375
 376                 switch (opcode) {
 377                 case TCPOPT_EOL:
 378                         return;
 379                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 380                         length--;
 381                         continue;
 382                 default:
 383                         if (length < 2)
 384                                 return;
 385                         opsize = *ptr++;
 386                         if (opsize < 2) /* "silly options" */
 387                                 return;
 388                         if (opsize > length)
 389                                 return; /* don't parse partial options */
 390                         if (opcode == TCPOPT_MPTCP)
 391                                 mptcp_parse_option(skb, ptr, opsize, mp_opt);
 392                         ptr += opsize - 2;
 393                         length -= opsize;
 394                 }
 395         }
 396 }
 397
 398 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 399                        unsigned int *size, struct mptcp_out_options *opts)
 400 {
 401         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 402
 403         /* we will use snd_isn to detect first pkt [re]transmission
 404          * in mptcp_established_options_mp()
 405          */
 406         subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
 407         if (subflow->request_mptcp) {
 408                 opts->suboptions = OPTION_MPTCP_MPC_SYN;
 409                 opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
 410                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 411                 *size = TCPOLEN_MPTCP_MPC_SYN;
 412                 return true;
 413         } else if (subflow->request_join) {
 414                 pr_debug("remote_token=%u, nonce=%u", subflow->remote_token,
 415                          subflow->local_nonce);
 416                 opts->suboptions = OPTION_MPTCP_MPJ_SYN;
 417                 opts->join_id = subflow->local_id;
 418                 opts->token = subflow->remote_token;
 419                 opts->nonce = subflow->local_nonce;
 420                 opts->backup = subflow->request_bkup;
 421                 *size = TCPOLEN_MPTCP_MPJ_SYN;
 422                 return true;
 423         }
 424         return false;
 425 }
 426
 427 static void clear_3rdack_retransmission(struct sock *sk)
 428 {
 429         struct inet_connection_sock *icsk = inet_csk(sk);
 430
 431         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 432         icsk->icsk_ack.timeout = 0;
 433         icsk->icsk_ack.ato = 0;
 434         icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 435 }
 436
 437 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 438                                          bool snd_data_fin_enable,
 439                                          unsigned int *size,
 440                                          unsigned int remaining,
 441                                          struct mptcp_out_options *opts)
 442 {
 443         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 444         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 445         struct mptcp_ext *mpext;
 446         unsigned int data_len;
 447         u8 len;
 448
 449         /* When skb is not available, we better over-estimate the emitted
 450          * options len. A full DSS option (28 bytes) is longer than
 451          * TCPOLEN_MPTCP_MPC_ACK_DATA(22) or TCPOLEN_MPTCP_MPJ_ACK(24), so
 452          * tell the caller to defer the estimate to
 453          * mptcp_established_options_dss(), which will reserve enough space.
 454          */
 455         if (!skb)
 456                 return false;
 457
 458         /* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
 459         if (subflow->fully_established || snd_data_fin_enable ||
 460             subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 461             sk->sk_state != TCP_ESTABLISHED)
 462                 return false;
 463
 464         if (subflow->mp_capable) {
 465                 mpext = mptcp_get_ext(skb);
 466                 data_len = mpext ? mpext->data_len : 0;
 467
 468                 /* we will check ops->data_len in mptcp_write_options() to
 469                  * discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
 470                  * TCPOLEN_MPTCP_MPC_ACK
 471                  */
 472                 opts->data_len = data_len;
 473                 opts->suboptions = OPTION_MPTCP_MPC_ACK;
 474                 opts->sndr_key = subflow->local_key;
 475                 opts->rcvr_key = subflow->remote_key;
 476                 opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 477                 opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
 478
 479                 /* Section 3.1.
 480                  * The MP_CAPABLE option is carried on the SYN, SYN/ACK, and ACK
 481                  * packets that start the first subflow of an MPTCP connection,
 482                  * as well as the first packet that carries data
 483                  */
 484                 if (data_len > 0) {
 485                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
 486                         if (opts->csum_reqd) {
 487                                 /* we need to propagate more info to csum the pseudo hdr */
 488                                 opts->data_seq = mpext->data_seq;
 489                                 opts->subflow_seq = mpext->subflow_seq;
 490                                 opts->csum = mpext->csum;
 491                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
 492                         }
 493                         *size = ALIGN(len, 4);
 494                 } else {
 495                         *size = TCPOLEN_MPTCP_MPC_ACK;
 496                 }
 497
 498                 pr_debug("subflow=%p, local_key=%llu, remote_key=%llu map_len=%d",
 499                          subflow, subflow->local_key, subflow->remote_key,
 500                          data_len);
 501
 502                 return true;
 503         } else if (subflow->mp_join) {
 504                 opts->suboptions = OPTION_MPTCP_MPJ_ACK;
 505                 memcpy(opts->hmac, subflow->hmac, MPTCPOPT_HMAC_LEN);
 506                 *size = TCPOLEN_MPTCP_MPJ_ACK;
 507                 pr_debug("subflow=%p", subflow);
 508
 509                 /* we can use the full delegate action helper only from BH context
 510                  * If we are in process context - sk is flushing the backlog at
 511                  * socket lock release time - just set the appropriate flag, will
 512                  * be handled by the release callback
 513                  */
 514                 if (sock_owned_by_user(sk))
 515                         set_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status);
 516                 else
 517                         mptcp_subflow_delegate(subflow, MPTCP_DELEGATE_ACK);
 518                 return true;
 519         }
 520         return false;
 521 }
 522
 523 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 524                                  struct sk_buff *skb, struct mptcp_ext *ext)
 525 {
 526         /* The write_seq value has already been incremented, so the actual
 527          * sequence number for the DATA_FIN is one less.
 528          */
 529         u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq) - 1;
 530
 531         if (!ext->use_map || !skb->len) {
 532                 /* RFC6824 requires a DSS mapping with specific values
 533                  * if DATA_FIN is set but no data payload is mapped
 534                  */
 535                 ext->data_fin = 1;
 536                 ext->use_map = 1;
 537                 ext->dsn64 = 1;
 538                 ext->data_seq = data_fin_tx_seq;
 539                 ext->subflow_seq = 0;
 540                 ext->data_len = 1;
 541         } else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 542                 /* If there's an existing DSS mapping and it is the
 543                  * final mapping, DATA_FIN consumes 1 additional byte of
 544                  * mapping space.
 545                  */
 546                 ext->data_fin = 1;
 547                 ext->data_len++;
 548         }
 549 }
 550
 551 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 552                                           bool snd_data_fin_enable,
 553                                           unsigned int *size,
 554                                           unsigned int remaining,
 555                                           struct mptcp_out_options *opts)
 556 {
 557         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 558         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 559         unsigned int dss_size = 0;
 560         struct mptcp_ext *mpext;
 561         unsigned int ack_size;
 562         bool ret = false;
 563         u64 ack_seq;
 564
 565         opts->csum_reqd = READ_ONCE(msk->csum_enabled);
 566         mpext = skb ? mptcp_get_ext(skb) : NULL;
 567
 568         if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 569                 unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 570
 571                 if (mpext) {
 572                         if (opts->csum_reqd)
 573                                 map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;
 574
 575                         opts->ext_copy = *mpext;
 576                 }
 577
 578                 remaining -= map_size;
 579                 dss_size = map_size;
 580                 if (skb && snd_data_fin_enable)
 581                         mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 582                 opts->suboptions = OPTION_MPTCP_DSS;
 583                 ret = true;
 584         }
 585
 586         /* passive sockets msk will set the 'can_ack' after accept(), even
 587          * if the first subflow may have the already the remote key handy
 588          */
 589         opts->ext_copy.use_ack = 0;
 590         if (!READ_ONCE(msk->can_ack)) {
 591                 *size = ALIGN(dss_size, 4);
 592                 return ret;
 593         }
 594
 595         ack_seq = READ_ONCE(msk->ack_seq);
 596         if (READ_ONCE(msk->use_64bit_ack)) {
 597                 ack_size = TCPOLEN_MPTCP_DSS_ACK64;
 598                 opts->ext_copy.data_ack = ack_seq;
 599                 opts->ext_copy.ack64 = 1;
 600         } else {
 601                 ack_size = TCPOLEN_MPTCP_DSS_ACK32;
 602                 opts->ext_copy.data_ack32 = (uint32_t)ack_seq;
 603                 opts->ext_copy.ack64 = 0;
 604         }
 605         opts->ext_copy.use_ack = 1;
 606         opts->suboptions = OPTION_MPTCP_DSS;
 607         WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
 608
 609         /* Add kind/length/subtype/flag overhead if mapping is not populated */
 610         if (dss_size == 0)
 611                 ack_size += TCPOLEN_MPTCP_DSS_BASE;
 612
 613         dss_size += ack_size;
 614
 615         *size = ALIGN(dss_size, 4);
 616         return true;
 617 }
 618
 619 static u64 add_addr_generate_hmac(u64 key1, u64 key2,
 620                                   struct mptcp_addr_info *addr)
 621 {
 622         u16 port = ntohs(addr->port);
 623         u8 hmac[SHA256_DIGEST_SIZE];
 624         u8 msg[19];
 625         int i = 0;
 626
 627         msg[i++] = addr->id;
 628         if (addr->family == AF_INET) {
 629                 memcpy(&msg[i], &addr->addr.s_addr, 4);
 630                 i += 4;
 631         }
 632 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 633         else if (addr->family == AF_INET6) {
 634                 memcpy(&msg[i], &addr->addr6.s6_addr, 16);
 635                 i += 16;
 636         }
 637 #endif
 638         msg[i++] = port >> 8;
 639         msg[i++] = port & 0xFF;
 640
 641         mptcp_crypto_hmac_sha(key1, key2, msg, i, hmac);
 642
 643         return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 644 }
 645
 646 static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
 647                                                unsigned int *size,
 648                                                unsigned int remaining,
 649                                                struct mptcp_out_options *opts)
 650 {
 651         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 652         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 653         bool drop_other_suboptions = false;
 654         unsigned int opt_size = *size;
 655         bool echo;
 656         int len;
 657
 658         /* add addr will strip the existing options, be sure to avoid breaking
 659          * MPC/MPJ handshakes
 660          */
 661         if (!mptcp_pm_should_add_signal(msk) ||
 662             (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||
 663             !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,
 664                     &echo, &drop_other_suboptions))
 665                 return false;
 666
 667         if (drop_other_suboptions)
 668                 remaining += opt_size;
 669         len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);
 670         if (remaining < len)
 671                 return false;
 672
 673         *size = len;
 674         if (drop_other_suboptions) {
 675                 pr_debug("drop other suboptions");
 676                 opts->suboptions = 0;
 677
 678                 /* note that e.g. DSS could have written into the memory
 679                  * aliased by ahmac, we must reset the field here
 680                  * to avoid appending the hmac even for ADD_ADDR echo
 681                  * options
 682                  */
 683                 opts->ahmac = 0;
 684                 *size -= opt_size;
 685         }
 686         opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
 687         if (!echo) {
 688                 opts->ahmac = add_addr_generate_hmac(msk->local_key,
 689                                                      msk->remote_key,
 690                                                      &opts->addr);
 691         }
 692         pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d",
 693                  opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port));
 694
 695         return true;
 696 }
 697
 698 static bool mptcp_established_options_rm_addr(struct sock *sk,
 699                                               unsigned int *size,
 700                                               unsigned int remaining,
 701                                               struct mptcp_out_options *opts)
 702 {
 703         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 704         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 705         struct mptcp_rm_list rm_list;
 706         int i, len;
 707
 708         if (!mptcp_pm_should_rm_signal(msk) ||
 709             !(mptcp_pm_rm_addr_signal(msk, remaining, &rm_list)))
 710                 return false;
 711
 712         len = mptcp_rm_addr_len(&rm_list);
 713         if (len < 0)
 714                 return false;
 715         if (remaining < len)
 716                 return false;
 717
 718         *size = len;
 719         opts->suboptions |= OPTION_MPTCP_RM_ADDR;
 720         opts->rm_list = rm_list;
 721
 722         for (i = 0; i < opts->rm_list.nr; i++)
 723                 pr_debug("rm_list_ids[%d]=%d", i, opts->rm_list.ids[i]);
 724
 725         return true;
 726 }
 727
 728 static bool mptcp_established_options_mp_prio(struct sock *sk,
 729                                               unsigned int *size,
 730                                               unsigned int remaining,
 731                                               struct mptcp_out_options *opts)
 732 {
 733         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 734
 735         /* can't send MP_PRIO with MPC, as they share the same option space:
 736          * 'backup'. Also it makes no sense at all
 737          */
 738         if (!subflow->send_mp_prio || (opts->suboptions & OPTIONS_MPTCP_MPC))
 739                 return false;
 740
 741         /* account for the trailing 'nop' option */
 742         if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN)
 743                 return false;
 744
 745         *size = TCPOLEN_MPTCP_PRIO_ALIGN;
 746         opts->suboptions |= OPTION_MPTCP_PRIO;
 747         opts->backup = subflow->request_bkup;
 748
 749         pr_debug("prio=%d", opts->backup);
 750
 751         return true;
 752 }
 753
 754 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
 755                                                    unsigned int *size,
 756                                                    unsigned int remaining,
 757                                                    struct mptcp_out_options *opts)
 758 {
 759         const struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 760
 761         if (remaining < TCPOLEN_MPTCP_RST)
 762                 return false;
 763
 764         *size = TCPOLEN_MPTCP_RST;
 765         opts->suboptions |= OPTION_MPTCP_RST;
 766         opts->reset_transient = subflow->reset_transient;
 767         opts->reset_reason = subflow->reset_reason;
 768         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTTX);
 769
 770         return true;
 771 }
 772
 773 static bool mptcp_established_options_fastclose(struct sock *sk,
 774                                                 unsigned int *size,
 775                                                 unsigned int remaining,
 776                                                 struct mptcp_out_options *opts)
 777 {
 778         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 779         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 780
 781         if (likely(!subflow->send_fastclose))
 782                 return false;
 783
 784         if (remaining < TCPOLEN_MPTCP_FASTCLOSE)
 785                 return false;
 786
 787         *size = TCPOLEN_MPTCP_FASTCLOSE;
 788         opts->suboptions |= OPTION_MPTCP_FASTCLOSE;
 789         opts->rcvr_key = msk->remote_key;
 790
 791         pr_debug("FASTCLOSE key=%llu", opts->rcvr_key);
 792         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSETX);
 793         return true;
 794 }
 795
 796 static bool mptcp_established_options_mp_fail(struct sock *sk,
 797                                               unsigned int *size,
 798                                               unsigned int remaining,
 799                                               struct mptcp_out_options *opts)
 800 {
 801         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 802
 803         if (likely(!subflow->send_mp_fail))
 804                 return false;
 805
 806         if (remaining < TCPOLEN_MPTCP_FAIL)
 807                 return false;
 808
 809         *size = TCPOLEN_MPTCP_FAIL;
 810         opts->suboptions |= OPTION_MPTCP_FAIL;
 811         opts->fail_seq = subflow->map_seq;
 812
 813         pr_debug("MP_FAIL fail_seq=%llu", opts->fail_seq);
 814         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
 815
 816         return true;
 817 }
 818
 819 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 820                                unsigned int *size, unsigned int remaining,
 821                                struct mptcp_out_options *opts)
 822 {
 823         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 824         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 825         unsigned int opt_size = 0;
 826         bool snd_data_fin;
 827         bool ret = false;
 828
 829         opts->suboptions = 0;
 830
 831         if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
 832                 return false;
 833
 834         if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 835                 if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
 836                     mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
 837                         *size += opt_size;
 838                         remaining -= opt_size;
 839                 }
 840                 /* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
 841                 if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
 842                         *size += opt_size;
 843                         remaining -= opt_size;
 844                 }
 845                 return true;
 846         }
 847
 848         snd_data_fin = mptcp_data_fin_enabled(msk);
 849         if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 850                 ret = true;
 851         else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts)) {
 852                 unsigned int mp_fail_size;
 853
 854                 ret = true;
 855                 if (mptcp_established_options_mp_fail(sk, &mp_fail_size,
 856                                                       remaining - opt_size, opts)) {
 857                         *size += opt_size + mp_fail_size;
 858                         remaining -= opt_size - mp_fail_size;
 859                         return true;
 860                 }
 861         }
 862
 863         /* we reserved enough space for the above options, and exceeding the
 864          * TCP option space would be fatal
 865          */
 866         if (WARN_ON_ONCE(opt_size > remaining))
 867                 return false;
 868
 869         *size += opt_size;
 870         remaining -= opt_size;
 871         if (mptcp_established_options_add_addr(sk, skb, &opt_size, remaining, opts)) {
 872                 *size += opt_size;
 873                 remaining -= opt_size;
 874                 ret = true;
 875         } else if (mptcp_established_options_rm_addr(sk, &opt_size, remaining, opts)) {
 876                 *size += opt_size;
 877                 remaining -= opt_size;
 878                 ret = true;
 879         }
 880
 881         if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
 882                 *size += opt_size;
 883                 remaining -= opt_size;
 884                 ret = true;
 885         }
 886
 887         return ret;
 888 }
 889
 890 bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 891                           struct mptcp_out_options *opts)
 892 {
 893         struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
 894
 895         if (subflow_req->mp_capable) {
 896                 opts->suboptions = OPTION_MPTCP_MPC_SYNACK;
 897                 opts->sndr_key = subflow_req->local_key;
 898                 opts->csum_reqd = subflow_req->csum_reqd;
 899                 opts->allow_join_id0 = subflow_req->allow_join_id0;
 900                 *size = TCPOLEN_MPTCP_MPC_SYNACK;
 901                 pr_debug("subflow_req=%p, local_key=%llu",
 902                          subflow_req, subflow_req->local_key);
 903                 return true;
 904         } else if (subflow_req->mp_join) {
 905                 opts->suboptions = OPTION_MPTCP_MPJ_SYNACK;
 906                 opts->backup = subflow_req->backup;
 907                 opts->join_id = subflow_req->local_id;
 908                 opts->thmac = subflow_req->thmac;
 909                 opts->nonce = subflow_req->local_nonce;
 910                 pr_debug("req=%p, bkup=%u, id=%u, thmac=%llu, nonce=%u",
 911                          subflow_req, opts->backup, opts->join_id,
 912                          opts->thmac, opts->nonce);
 913                 *size = TCPOLEN_MPTCP_MPJ_SYNACK;
 914                 return true;
 915         }
 916         return false;
 917 }
 918
 919 static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 920                                     struct mptcp_subflow_context *subflow,
 921                                     struct sk_buff *skb,
 922                                     struct mptcp_options_received *mp_opt)
 923 {
 924         /* here we can process OoO, in-window pkts, only in-sequence 4th ack
 925          * will make the subflow fully established
 926          */
 927         if (likely(subflow->fully_established)) {
 928                 /* on passive sockets, check for 3rd ack retransmission
 929                  * note that msk is always set by subflow_syn_recv_sock()
 930                  * for mp_join subflows
 931                  */
 932                 if (TCP_SKB_CB(skb)->seq == subflow->ssn_offset + 1 &&
 933                     TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq &&
 934                     subflow->mp_join && (mp_opt->suboptions & OPTIONS_MPTCP_MPJ) &&
 935                     !subflow->request_join)
 936                         tcp_send_ack(ssk);
 937                 goto fully_established;
 938         }
 939
 940         /* we must process OoO packets before the first subflow is fully
 941          * established. OoO packets are instead a protocol violation
 942          * for MP_JOIN subflows as the peer must not send any data
 943          * before receiving the forth ack - cfr. RFC 8684 section 3.2.
 944          */
 945         if (TCP_SKB_CB(skb)->seq != subflow->ssn_offset + 1) {
 946                 if (subflow->mp_join)
 947                         goto reset;
 948                 return subflow->mp_capable;
 949         }
 950
 951         if (((mp_opt->suboptions & OPTION_MPTCP_DSS) && mp_opt->use_ack) ||
 952             ((mp_opt->suboptions & OPTION_MPTCP_ADD_ADDR) && !mp_opt->echo)) {
 953                 /* subflows are fully established as soon as we get any
 954                  * additional ack, including ADD_ADDR.
 955                  */
 956                 subflow->fully_established = 1;
 957                 WRITE_ONCE(msk->fully_established, true);
 958                 goto fully_established;
 959         }
 960
 961         /* If the first established packet does not contain MP_CAPABLE + data
 962          * then fallback to TCP. Fallback scenarios requires a reset for
 963          * MP_JOIN subflows.
 964          */
 965         if (!(mp_opt->suboptions & OPTIONS_MPTCP_MPC)) {
 966                 if (subflow->mp_join)
 967                         goto reset;
 968                 subflow->mp_capable = 0;
 969                 pr_fallback(msk);
 970                 mptcp_do_fallback(ssk);
 971                 return false;
 972         }
 973
 974         if (mp_opt->deny_join_id0)
 975                 WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
 976
 977         if (unlikely(!READ_ONCE(msk->pm.server_side)))
 978                 pr_warn_once("bogus mpc option on established client sk");
 979         mptcp_subflow_fully_established(subflow, mp_opt);
 980
 981 fully_established:
 982         /* if the subflow is not already linked into the conn_list, we can't
 983          * notify the PM: this subflow is still on the listener queue
 984          * and the PM possibly acquiring the subflow lock could race with
 985          * the listener close
 986          */
 987         if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 988                 return true;
 989
 990         subflow->pm_notified = 1;
 991         if (subflow->mp_join) {
 992                 clear_3rdack_retransmission(ssk);
 993                 mptcp_pm_subflow_established(msk);
 994         } else {
 995                 mptcp_pm_fully_established(msk, ssk, GFP_ATOMIC);
 996         }
 997         return true;
 998
 999 reset:
1000         mptcp_subflow_reset(ssk);
1001         return false;
1002 }
1003
1004 u64 __mptcp_expand_seq(u64 old_seq, u64 cur_seq)
1005 {
1006         u32 old_seq32, cur_seq32;
1007
1008         old_seq32 = (u32)old_seq;
1009         cur_seq32 = (u32)cur_seq;
1010         cur_seq = (old_seq & GENMASK_ULL(63, 32)) + cur_seq32;
1011         if (unlikely(cur_seq32 < old_seq32 && before(old_seq32, cur_seq32)))
1012                 return cur_seq + (1LL << 32);
1013
1014         /* reverse wrap could happen, too */
1015         if (unlikely(cur_seq32 > old_seq32 && after(old_seq32, cur_seq32)))
1016                 return cur_seq - (1LL << 32);
1017         return cur_seq;
1018 }
1019
1020 static void ack_update_msk(struct mptcp_sock *msk,
1021                            struct sock *ssk,
1022                            struct mptcp_options_received *mp_opt)
1023 {
1024         u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt);
1025         struct sock *sk = (struct sock *)msk;
1026         u64 old_snd_una;
1027
1028         mptcp_data_lock(sk);
1029
1030         /* avoid ack expansion on update conflict, to reduce the risk of
1031          * wrongly expanding to a future ack sequence number, which is way
1032          * more dangerous than missing an ack
1033          */
1034         old_snd_una = msk->snd_una;
1035         new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
1036
1037         /* ACK for data not even sent yet? Ignore.*/
1038         if (unlikely(after64(new_snd_una, snd_nxt)))
1039                 new_snd_una = old_snd_una;
1040
1041         new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;
1042
1043         if (after64(new_wnd_end, msk->wnd_end))
1044                 msk->wnd_end = new_wnd_end;
1045
1046         /* this assumes mptcp_incoming_options() is invoked after tcp_ack() */
1047         if (after64(msk->wnd_end, READ_ONCE(msk->snd_nxt)))
1048                 __mptcp_check_push(sk, ssk);
1049
1050         if (after64(new_snd_una, old_snd_una)) {
1051                 msk->snd_una = new_snd_una;
1052                 __mptcp_data_acked(sk);
1053         }
1054         mptcp_data_unlock(sk);
1055
1056         trace_ack_update_msk(mp_opt->data_ack,
1057                              old_snd_una, new_snd_una,
1058                              new_wnd_end, msk->wnd_end);
1059 }
1060
1061 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit)
1062 {
1063         /* Skip if DATA_FIN was already received.
1064          * If updating simultaneously with the recvmsg loop, values
1065          * should match. If they mismatch, the peer is misbehaving and
1066          * we will prefer the most recent information.
1067          */
1068         if (READ_ONCE(msk->rcv_data_fin))
1069                 return false;
1070
1071         WRITE_ONCE(msk->rcv_data_fin_seq,
1072                    mptcp_expand_seq(READ_ONCE(msk->ack_seq), data_fin_seq, use_64bit));
1073         WRITE_ONCE(msk->rcv_data_fin, 1);
1074
1075         return true;
1076 }
1077
1078 static bool add_addr_hmac_valid(struct mptcp_sock *msk,
1079                                 struct mptcp_options_received *mp_opt)
1080 {
1081         u64 hmac = 0;
1082
1083         if (mp_opt->echo)
1084                 return true;
1085
1086         hmac = add_addr_generate_hmac(msk->remote_key,
1087                                       msk->local_key,
1088                                       &mp_opt->addr);
1089
1090         pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
1091                  msk, hmac, mp_opt->ahmac);
1092
1093         return hmac == mp_opt->ahmac;
1094 }
1095
1096 /* Return false if a subflow has been reset, else return true */
1097 bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
1098 {
1099         struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
1100         struct mptcp_sock *msk = mptcp_sk(subflow->conn);
1101         struct mptcp_options_received mp_opt;
1102         struct mptcp_ext *mpext;
1103
1104         if (__mptcp_check_fallback(msk)) {
1105                 /* Keep it simple and unconditionally trigger send data cleanup and
1106                  * pending queue spooling. We will need to acquire the data lock
1107                  * for more accurate checks, and once the lock is acquired, such
1108                  * helpers are cheap.
1109                  */
1110                 mptcp_data_lock(subflow->conn);
1111                 if (sk_stream_memory_free(sk))
1112                         __mptcp_check_push(subflow->conn, sk);
1113                 __mptcp_data_acked(subflow->conn);
1114                 mptcp_data_unlock(subflow->conn);
1115                 return true;
1116         }
1117
1118         mptcp_get_options(skb, &mp_opt);
1119
1120         /* The subflow can be in close state only if check_fully_established()
1121          * just sent a reset. If so, tell the caller to ignore the current packet.
1122          */
1123         if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
1124                 return sk->sk_state != TCP_CLOSE;
1125
1126         if (unlikely(mp_opt.suboptions != OPTION_MPTCP_DSS)) {
1127                 if ((mp_opt.suboptions & OPTION_MPTCP_FASTCLOSE) &&
1128                     msk->local_key == mp_opt.rcvr_key) {
1129                         WRITE_ONCE(msk->rcv_fastclose, true);
1130                         mptcp_schedule_work((struct sock *)msk);
1131                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFASTCLOSERX);
1132                 }
1133
1134                 if ((mp_opt.suboptions & OPTION_MPTCP_ADD_ADDR) &&
1135                     add_addr_hmac_valid(msk, &mp_opt)) {
1136                         if (!mp_opt.echo) {
1137                                 mptcp_pm_add_addr_received(sk, &mp_opt.addr);
1138                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDR);
1139                         } else {
1140                                 mptcp_pm_add_addr_echoed(msk, &mp_opt.addr);
1141                                 mptcp_pm_del_add_timer(msk, &mp_opt.addr, true);
1142                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADD);
1143                         }
1144
1145                         if (mp_opt.addr.port)
1146                                 MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_PORTADD);
1147                 }
1148
1149                 if (mp_opt.suboptions & OPTION_MPTCP_RM_ADDR)
1150                         mptcp_pm_rm_addr_received(msk, &mp_opt.rm_list);
1151
1152                 if (mp_opt.suboptions & OPTION_MPTCP_PRIO) {
1153                         mptcp_pm_mp_prio_received(sk, mp_opt.backup);
1154                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIORX);
1155                 }
1156
1157                 if (mp_opt.suboptions & OPTION_MPTCP_FAIL) {
1158                         mptcp_pm_mp_fail_received(sk, mp_opt.fail_seq);
1159                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILRX);
1160                 }
1161
1162                 if (mp_opt.suboptions & OPTION_MPTCP_RST) {
1163                         subflow->reset_seen = 1;
1164                         subflow->reset_reason = mp_opt.reset_reason;
1165                         subflow->reset_transient = mp_opt.reset_transient;
1166                         MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPRSTRX);
1167                 }
1168
1169                 if (!(mp_opt.suboptions & OPTION_MPTCP_DSS))
1170                         return true;
1171         }
1172
1173         /* we can't wait for recvmsg() to update the ack_seq, otherwise
1174          * monodirectional flows will stuck
1175          */
1176         if (mp_opt.use_ack)
1177                 ack_update_msk(msk, sk, &mp_opt);
1178
1179         /* Zero-data-length packets are dropped by the caller and not
1180          * propagated to the MPTCP layer, so the skb extension does not
1181          * need to be allocated or populated. DATA_FIN information, if
1182          * present, needs to be updated here before the skb is freed.
1183          */
1184         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
1185                 if (mp_opt.data_fin && mp_opt.data_len == 1 &&
1186                     mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64) &&
1187                     schedule_work(&msk->work))
1188                         sock_hold(subflow->conn);
1189
1190                 return true;
1191         }
1192
1193         mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
1194         if (!mpext)
1195                 return true;
1196
1197         memset(mpext, 0, sizeof(*mpext));
1198
1199         if (likely(mp_opt.use_map)) {
1200                 if (mp_opt.mpc_map) {
1201                         /* this is an MP_CAPABLE carrying MPTCP data
1202                          * we know this map the first chunk of data
1203                          */
1204                         mptcp_crypto_key_sha(subflow->remote_key, NULL,
1205                                              &mpext->data_seq);
1206                         mpext->data_seq++;
1207                         mpext->subflow_seq = 1;
1208                         mpext->dsn64 = 1;
1209                         mpext->mpc_map = 1;
1210                         mpext->data_fin = 0;
1211                 } else {
1212                         mpext->data_seq = mp_opt.data_seq;
1213                         mpext->subflow_seq = mp_opt.subflow_seq;
1214                         mpext->dsn64 = mp_opt.dsn64;
1215                         mpext->data_fin = mp_opt.data_fin;
1216                 }
1217                 mpext->data_len = mp_opt.data_len;
1218                 mpext->use_map = 1;
1219                 mpext->csum_reqd = !!(mp_opt.suboptions & OPTION_MPTCP_CSUMREQD);
1220
1221                 if (mpext->csum_reqd)
1222                         mpext->csum = mp_opt.csum;
1223         }
1224
1225         return true;
1226 }
1227
1228 static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th)
1229 {
1230         const struct sock *ssk = (const struct sock *)tp;
1231         struct mptcp_subflow_context *subflow;
1232         u64 ack_seq, rcv_wnd_old, rcv_wnd_new;
1233         struct mptcp_sock *msk;
1234         u32 new_win;
1235         u64 win;
1236
1237         subflow = mptcp_subflow_ctx(ssk);
1238         msk = mptcp_sk(subflow->conn);
1239
1240         ack_seq = READ_ONCE(msk->ack_seq);
1241         rcv_wnd_new = ack_seq + tp->rcv_wnd;
1242
1243         rcv_wnd_old = atomic64_read(&msk->rcv_wnd_sent);
1244         if (after64(rcv_wnd_new, rcv_wnd_old)) {
1245                 u64 rcv_wnd;
1246
1247                 for (;;) {
1248                         rcv_wnd = atomic64_cmpxchg(&msk->rcv_wnd_sent, rcv_wnd_old, rcv_wnd_new);
1249
1250                         if (rcv_wnd == rcv_wnd_old)
1251                                 break;
1252                         if (before64(rcv_wnd_new, rcv_wnd)) {
1253                                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICTUPDATE);
1254                                 goto raise_win;
1255                         }
1256                         MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDCONFLICT);
1257                         rcv_wnd_old = rcv_wnd;
1258                 }
1259                 return;
1260         }
1261
1262         if (rcv_wnd_new != rcv_wnd_old) {
1263 raise_win:
1264                 win = rcv_wnd_old - ack_seq;
1265                 tp->rcv_wnd = min_t(u64, win, U32_MAX);
1266                 new_win = tp->rcv_wnd;
1267
1268                 /* Make sure we do not exceed the maximum possible
1269                  * scaled window.
1270                  */
1271                 if (unlikely(th->syn))
1272                         new_win = min(new_win, 65535U) << tp->rx_opt.rcv_wscale;
1273                 if (!tp->rx_opt.rcv_wscale &&
1274                     READ_ONCE(sock_net(ssk)->ipv4.sysctl_tcp_workaround_signed_windows))
1275                         new_win = min(new_win, MAX_TCP_WINDOW);
1276                 else
1277                         new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
1278
1279                 /* RFC1323 scaling applied */
1280                 new_win >>= tp->rx_opt.rcv_wscale;
1281                 th->window = htons(new_win);
1282                 MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_RCVWNDSHARED);
1283         }
1284 }
1285
1286 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
1287 {
1288         struct csum_pseudo_header header;
1289         __wsum csum;
1290
1291         /* cfr RFC 8684 3.3.1.:
1292          * the data sequence number used in the pseudo-header is
1293          * always the 64-bit value, irrespective of what length is used in the
1294          * DSS option itself.
1295          */
1296         header.data_seq = cpu_to_be64(data_seq);
1297         header.subflow_seq = htonl(subflow_seq);
1298         header.data_len = htons(data_len);
1299         header.csum = 0;
1300
1301         csum = csum_partial(&header, sizeof(header), sum);
1302         return csum_fold(csum);
1303 }
1304
1305 static __sum16 mptcp_make_csum(const struct mptcp_ext *mpext)
1306 {
1307         return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
1308                                  ~csum_unfold(mpext->csum));
1309 }
1310
1311 static void put_len_csum(u16 len, __sum16 csum, void *data)
1312 {
1313         __sum16 *sumptr = data + 2;
1314         __be16 *ptr = data;
1315
1316         put_unaligned_be16(len, ptr);
1317
1318         put_unaligned(csum, sumptr);
1319 }
1320
1321 void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
1322                          struct mptcp_out_options *opts)
1323 {
1324         const struct sock *ssk = (const struct sock *)tp;
1325         struct mptcp_subflow_context *subflow;
1326
1327         /* Which options can be used together?
1328          *
1329          * X: mutually exclusive
1330          * O: often used together
1331          * C: can be used together in some cases
1332          * P: could be used together but we prefer not to (optimisations)
1333          *
1334          *  Opt: | MPC  | MPJ  | DSS  | ADD  |  RM  | PRIO | FAIL |  FC  |
1335          * ------|------|------|------|------|------|------|------|------|
1336          *  MPC  |------|------|------|------|------|------|------|------|
1337          *  MPJ  |  X   |------|------|------|------|------|------|------|
1338          *  DSS  |  X   |  X   |------|------|------|------|------|------|
1339          *  ADD  |  X   |  X   |  P   |------|------|------|------|------|
1340          *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
1341          *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
1342          *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
1343          *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
1344          *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
1345          * ------|------|------|------|------|------|------|------|------|
1346          *
1347          * The same applies in mptcp_established_options() function.
1348          */
1349         if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
1350                 struct mptcp_ext *mpext = &opts->ext_copy;
1351                 u8 len = TCPOLEN_MPTCP_DSS_BASE;
1352                 u8 flags = 0;
1353
1354                 if (mpext->use_ack) {
1355                         flags = MPTCP_DSS_HAS_ACK;
1356                         if (mpext->ack64) {
1357                                 len += TCPOLEN_MPTCP_DSS_ACK64;
1358                                 flags |= MPTCP_DSS_ACK64;
1359                         } else {
1360                                 len += TCPOLEN_MPTCP_DSS_ACK32;
1361                         }
1362                 }
1363
1364                 if (mpext->use_map) {
1365                         len += TCPOLEN_MPTCP_DSS_MAP64;
1366
1367                         /* Use only 64-bit mapping flags for now, add
1368                          * support for optional 32-bit mappings later.
1369                          */
1370                         flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
1371                         if (mpext->data_fin)
1372                                 flags |= MPTCP_DSS_DATA_FIN;
1373
1374                         if (opts->csum_reqd)
1375                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1376                 }
1377
1378                 *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
1379
1380                 if (mpext->use_ack) {
1381                         if (mpext->ack64) {
1382                                 put_unaligned_be64(mpext->data_ack, ptr);
1383                                 ptr += 2;
1384                         } else {
1385                                 put_unaligned_be32(mpext->data_ack32, ptr);
1386                                 ptr += 1;
1387                         }
1388                 }
1389
1390                 if (mpext->use_map) {
1391                         put_unaligned_be64(mpext->data_seq, ptr);
1392                         ptr += 2;
1393                         put_unaligned_be32(mpext->subflow_seq, ptr);
1394                         ptr += 1;
1395                         if (opts->csum_reqd) {
1396                                 /* data_len == 0 is reserved for the infinite mapping,
1397                                  * the checksum will also be set to 0.
1398                                  */
1399                                 put_len_csum(mpext->data_len,
1400                                              (mpext->data_len ? mptcp_make_csum(mpext) : 0),
1401                                              ptr);
1402                         } else {
1403                                 put_unaligned_be32(mpext->data_len << 16 |
1404                                                    TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1405                         }
1406                         ptr += 1;
1407                 }
1408
1409                 /* We might need to add MP_FAIL options in rare cases */
1410                 if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions))
1411                         goto mp_fail;
1412         } else if (OPTIONS_MPTCP_MPC & opts->suboptions) {
1413                 u8 len, flag = MPTCP_CAP_HMAC_SHA256;
1414
1415                 if (OPTION_MPTCP_MPC_SYN & opts->suboptions) {
1416                         len = TCPOLEN_MPTCP_MPC_SYN;
1417                 } else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
1418                         len = TCPOLEN_MPTCP_MPC_SYNACK;
1419                 } else if (opts->data_len) {
1420                         len = TCPOLEN_MPTCP_MPC_ACK_DATA;
1421                         if (opts->csum_reqd)
1422                                 len += TCPOLEN_MPTCP_DSS_CHECKSUM;
1423                 } else {
1424                         len = TCPOLEN_MPTCP_MPC_ACK;
1425                 }
1426
1427                 if (opts->csum_reqd)
1428                         flag |= MPTCP_CAP_CHECKSUM_REQD;
1429
1430                 if (!opts->allow_join_id0)
1431                         flag |= MPTCP_CAP_DENY_JOIN_ID0;
1432
1433                 *ptr++ = mptcp_option(MPTCPOPT_MP_CAPABLE, len,
1434                                       MPTCP_SUPPORTED_VERSION,
1435                                       flag);
1436
1437                 if (!((OPTION_MPTCP_MPC_SYNACK | OPTION_MPTCP_MPC_ACK) &
1438                     opts->suboptions))
1439                         goto mp_capable_done;
1440
1441                 put_unaligned_be64(opts->sndr_key, ptr);
1442                 ptr += 2;
1443                 if (!((OPTION_MPTCP_MPC_ACK) & opts->suboptions))
1444                         goto mp_capable_done;
1445
1446                 put_unaligned_be64(opts->rcvr_key, ptr);
1447                 ptr += 2;
1448                 if (!opts->data_len)
1449                         goto mp_capable_done;
1450
1451                 if (opts->csum_reqd) {
1452                         put_len_csum(opts->data_len,
1453                                      __mptcp_make_csum(opts->data_seq,
1454                                                        opts->subflow_seq,
1455                                                        opts->data_len,
1456                                                        ~csum_unfold(opts->csum)),
1457                                      ptr);
1458                 } else {
1459                         put_unaligned_be32(opts->data_len << 16 |
1460                                            TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
1461                 }
1462                 ptr += 1;
1463
1464                 /* MPC is additionally mutually exclusive with MP_PRIO */
1465                 goto mp_capable_done;
1466         } else if (OPTIONS_MPTCP_MPJ & opts->suboptions) {
1467                 if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
1468                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1469                                               TCPOLEN_MPTCP_MPJ_SYN,
1470                                               opts->backup, opts->join_id);
1471                         put_unaligned_be32(opts->token, ptr);
1472                         ptr += 1;
1473                         put_unaligned_be32(opts->nonce, ptr);
1474                         ptr += 1;
1475                 } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
1476                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1477                                               TCPOLEN_MPTCP_MPJ_SYNACK,
1478                                               opts->backup, opts->join_id);
1479                         put_unaligned_be64(opts->thmac, ptr);
1480                         ptr += 2;
1481                         put_unaligned_be32(opts->nonce, ptr);
1482                         ptr += 1;
1483                 } else {
1484                         *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
1485                                               TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
1486                         memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
1487                         ptr += 5;
1488                 }
1489         } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
1490                 u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
1491                 u8 echo = MPTCP_ADDR_ECHO;
1492
1493 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1494                 if (opts->addr.family == AF_INET6)
1495                         len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
1496 #endif
1497
1498                 if (opts->addr.port)
1499                         len += TCPOLEN_MPTCP_PORT_LEN;
1500
1501                 if (opts->ahmac) {
1502                         len += sizeof(opts->ahmac);
1503                         echo = 0;
1504                 }
1505
1506                 *ptr++ = mptcp_option(MPTCPOPT_ADD_ADDR,
1507                                       len, echo, opts->addr.id);
1508                 if (opts->addr.family == AF_INET) {
1509                         memcpy((u8 *)ptr, (u8 *)&opts->addr.addr.s_addr, 4);
1510                         ptr += 1;
1511                 }
1512 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
1513                 else if (opts->addr.family == AF_INET6) {
1514                         memcpy((u8 *)ptr, opts->addr.addr6.s6_addr, 16);
1515                         ptr += 4;
1516                 }
1517 #endif
1518
1519                 if (!opts->addr.port) {
1520                         if (opts->ahmac) {
1521                                 put_unaligned_be64(opts->ahmac, ptr);
1522                                 ptr += 2;
1523                         }
1524                 } else {
1525                         u16 port = ntohs(opts->addr.port);
1526
1527                         if (opts->ahmac) {
1528                                 u8 *bptr = (u8 *)ptr;
1529
1530                                 put_unaligned_be16(port, bptr);
1531                                 bptr += 2;
1532                                 put_unaligned_be64(opts->ahmac, bptr);
1533                                 bptr += 8;
1534                                 put_unaligned_be16(TCPOPT_NOP << 8 |
1535                                                    TCPOPT_NOP, bptr);
1536
1537                                 ptr += 3;
1538                         } else {
1539                                 put_unaligned_be32(port << 16 |
1540                                                    TCPOPT_NOP << 8 |
1541                                                    TCPOPT_NOP, ptr);
1542                                 ptr += 1;
1543                         }
1544                 }
1545         } else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
1546                 /* FASTCLOSE is mutually exclusive with others except RST */
1547                 *ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
1548                                       TCPOLEN_MPTCP_FASTCLOSE,
1549                                       0, 0);
1550                 put_unaligned_be64(opts->rcvr_key, ptr);
1551                 ptr += 2;
1552
1553                 if (OPTION_MPTCP_RST & opts->suboptions)
1554                         goto mp_rst;
1555                 return;
1556         } else if (unlikely(OPTION_MPTCP_FAIL & opts->suboptions)) {
1557 mp_fail:
1558                 /* MP_FAIL is mutually exclusive with others except RST */
1559                 subflow = mptcp_subflow_ctx(ssk);
1560                 subflow->send_mp_fail = 0;
1561
1562                 *ptr++ = mptcp_option(MPTCPOPT_MP_FAIL,
1563                                       TCPOLEN_MPTCP_FAIL,
1564                                       0, 0);
1565                 put_unaligned_be64(opts->fail_seq, ptr);
1566                 ptr += 2;
1567
1568                 if (OPTION_MPTCP_RST & opts->suboptions)
1569                         goto mp_rst;
1570                 return;
1571         } else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
1572 mp_rst:
1573                 *ptr++ = mptcp_option(MPTCPOPT_RST,
1574                                       TCPOLEN_MPTCP_RST,
1575                                       opts->reset_transient,
1576                                       opts->reset_reason);
1577                 return;
1578         }
1579
1580         if (OPTION_MPTCP_PRIO & opts->suboptions) {
1581                 subflow = mptcp_subflow_ctx(ssk);
1582                 subflow->send_mp_prio = 0;
1583
1584                 *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
1585                                       TCPOLEN_MPTCP_PRIO,
1586                                       opts->backup, TCPOPT_NOP);
1587
1588                 MPTCP_INC_STATS(sock_net((const struct sock *)tp),
1589                                 MPTCP_MIB_MPPRIOTX);
1590         }
1591
1592 mp_capable_done:
1593         if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
1594                 u8 i = 1;
1595
1596                 *ptr++ = mptcp_option(MPTCPOPT_RM_ADDR,
1597                                       TCPOLEN_MPTCP_RM_ADDR_BASE + opts->rm_list.nr,
1598                                       0, opts->rm_list.ids[0]);
1599
1600                 while (i < opts->rm_list.nr) {
1601                         u8 id1, id2, id3, id4;
1602
1603                         id1 = opts->rm_list.ids[i];
1604                         id2 = i + 1 < opts->rm_list.nr ? opts->rm_list.ids[i + 1] : TCPOPT_NOP;
1605                         id3 = i + 2 < opts->rm_list.nr ? opts->rm_list.ids[i + 2] : TCPOPT_NOP;
1606                         id4 = i + 3 < opts->rm_list.nr ? opts->rm_list.ids[i + 3] : TCPOPT_NOP;
1607                         put_unaligned_be32(id1 << 24 | id2 << 16 | id3 << 8 | id4, ptr);
1608                         ptr += 1;
1609                         i += 4;
1610                 }
1611         }
1612
1613         if (tp)
1614                 mptcp_set_rwin(tp, th);
1615 }
1616
1617 __be32 mptcp_get_reset_option(const struct sk_buff *skb)
1618 {
1619         const struct mptcp_ext *ext = mptcp_get_ext(skb);
1620         u8 flags, reason;
1621
1622         if (ext) {
1623                 flags = ext->reset_transient;
1624                 reason = ext->reset_reason;
1625
1626                 return mptcp_option(MPTCPOPT_RST, TCPOLEN_MPTCP_RST,
1627                                     flags, reason);
1628         }
1629
1630         return htonl(0u);
1631 }
1632 EXPORT_SYMBOL_GPL(mptcp_get_reset_option);